Soybean [Glycine max L. (Merrill)] is a major oil seed crop and is grown throughout much of the world. The United States alone produces over half of the world output. Soybean seed typically contains 40% protein and 20% oil and is used primarily for livestock feed and industrial purposes, in addition to human consumption. Soybeans are a major cash crop and investment commodity in North America and elsewhere. Soybean oil is one of the most widely used edible oils, and soybeans are used worldwide both in animal feed and in human food production.
Soybean sudden death syndrome (SDS) is a fungal disease of soybean (Glycine max (L.)), caused by Fusarium solani. Since its discovery SDS has become one of the most destructive pests in soybean. It has been reported in nearly all states that soybean are grown, and it causes production problems in several states, being particularly destructive in Midwestern states. See generally (Mulrooney 1988, Gibson et al., 1994, Hartman et al., 1995, Wrather et al., 1995, 1996). Nationwide, the estimated soybean yield suppression from SDS in 2010 was 2.1% of total yield valued at $0.82 billion. In certain years, SDS causes total crop loss in many soybean fields.
Although the use of fungicides is effective in reducing the population level of the fungus, fungicide use is both uneconomical and environmentally unsound as a control measure in soybean production. Neither is crop rotation a practical means of fungal control since rotation with a non-susceptible crop for at least two years is necessary for reducing soybean losses. Therefore, soybean breeders generally rely on the use of resistant varieties as the most practical control measure.
Resistance generally means the ability of a plant to prevent, or at least curtail the infestation and colonization by a harmful pathogen. Different mechanisms can be discerned in the naturally occurring resistance, with which the plants fend off colonization by phytopathogenic organisms. These specific interactions between the pathogen and the host determine the course of infection (Schopfer and Brennicke (1999) flanzenphysiologie, Springer Verlag, Berlin-Heidelberg, Germany).
Resistance to SDS is multigenic and quantitative in soybean (Hnetkovsky et al., 1996; Njiti et al., 1996). Chang et al., (1996, 1997) estimated that Forrest has 5 genes required for resistance to SDS. Njiti et al., (1996) and Kilo et al., (1996) estimated that Pyramid has genes required for resistance to SDS, 2 that were different from those in Forrest. The multiple genes and genetic backgrounds involved contribute to the difficulty breeders have in developing SDS resistant soybean varieties.
It is an object of the present invention to identify and use Fusarium resistance genes to engineer or improve SDS resistance in susceptible host plants.
Spider mites are yield-reducing pests in soybean, which feed on the abaxial surface of leaves, and produce symptoms such as yellowing and whitish spot, bronzing, and webbing on the adaxial side of leaves. These symptoms are mostly severe, as these tinny insects multiply very quickly, with one generation being completed as short as in 5 to 8 days (English-Loeb et al., 1998; Shurtleff and Aoyagi, 2009; Scranton et al., 2013). Unfortunately, fewer studies have focused on identifying mite resistant genes.
As can be seen a need exists for identifying and using mite resistant genes to engineer or improve resistance in susceptible host plants.
Soybean aphid, (Aphis glycines, Matsumura) is among the major yield-reducing pests of soybean (Zuang et al., 2002). Aphis glycines Matsumura, was identified as new insect pest of soybeans in 2001 and spread to over 21 states in the United States and 3 Canadian provinces by 2003 (Vennette et al. Ann Entomol Soc Am 97:217-226 (2004)). High yields are critical to a farmer's profit margin. Soybean aphid can cause over 50% yield losses (Wang et al., Plant Protect 20:12-13 (1994)). In addition to the decrease in yield, an increase in insecticide use can also decrease a farmer's profit margin. Over 7 million acres of soybean in the North Central U.S. were sprayed with insecticide to control soybean aphids in 2003; the estimated cost of the insecticide treatments was $84-$105 million in the North Central region alone in 2003 (Landis et al. NCR-125 Arthropod biological control: state reports for 2003; Li et al., Mol Breeding 19:25-34 (2007)).
It is a further object of the present invention to identify and use aphid resistance genes to engineer or improve SDS resistance in susceptible host plants.
The soybean cyst nematode (SCN), Heterodera glycines, is a very serious soybean pest. Female nematodes attack and feed in soybean roots leading to death of the entire plants and therefore severe yield losses occur across the globe (Koenning et al., 2012). Fortunately, genes conferring SCN resistance are deployed to create SCN resistant cultivars to protect the crop losses. Two of these genes have been recently isolated; and both encode distinct novel mechanisms (Cook et al., 2012; Liu et al., 2012). However, there remains a need for identifying and using SCN resistant genes to engineer or improve SCN resistance in susceptible host plants.
Other objects will become apparent from the description of the invention which follows.